Other Physics Commons^™

High-Pressure High-Temperature Exploration Of Phase Boundaries Using Raman Spectroscopy, Jasmine Kashmir Hinton

UNLV Theses, Dissertations, Professional Papers, and Capstones

Metastability of states can provide interesting properties that may not be readily accessible in a material’s ground state. Many materials show high levels of polymorphism, indicating a rich energy landscape and a potential for metastable states. Melt crystallization techniques provide a potential route to these states. We use a resistively heated diamond anvil cell (DAC) with fine control of a system’s pressure and temperature to explore these systems. Raman spectroscopy is used to track subtle structural changes across phase boundaries. Organic systems, such as glycine and aspirin, were our initial interest due to their high polymorphism and reported low melting …

The Population Densities Of Argon Metastable Levels, Nada Khogeer, Chelsy Gonzalez, Milka Nikolic

Physics and Astronomy

In this experiment, we used the optical emission spectroscopy (OES) method to obtain the main properties of low temperature Argon plasma. The experiment was sustained in powers and pressures that ranges from 30-100 W and 15-100 mTorr. We used numerical methods for the Argon kinetic model to calculate metastable levels and resonant states for the first excited states in low temperature Argon plasma. By finding the ratio of two spectral lines and finding another ratio from a different upper energy level that goes down to the same two lower energy levels, we can construct a system of two nonlinear equations. …

Origin Of Enhanced Anisotropy In Fept-C Granular Films Revealed By Xmcd, Robert Streubel, Alpha T. N'Diaye, Kumar Srinivasan, Antony Ajan, Peter Fischer

Robert Streubel Papers

We study the effect of carbon segregants on the spin and orbital moments of L10 FePt granular media using x-ray magnetic circular dichroism (XMCD) spectroscopy and report an effective decoupling of the structural film properties from the magnetic parameters of the grains. The carbon concentration reduces the grain size from (200 ± 160) nm2 down to (50 ± 20) nm2 for 40 mol. %C and improves sphericity and the order of grains, while preserving the crystalline order, spin and orbital moments, and perpendicular magnetocrystalline anisotropy. We identify the primary cause of enhanced saturation and coercive fields as the reduced demagnetization …

Evaluation Of Ventilation Assistance For Improving Respiratory Reproducibility In Radiation Therapy, Cameron J. Sprowls

LSU Master's Theses

Background: Respiratory motion affects all tumor sites in the thorax and abdomen. Variations of the respiratory pattern cause variations of the tumor motion which can result in differences between the planned and delivered dose distributions. Previous breathing guidance techniques have been investigated to improve respiratory reproducibility; however, ventilation assistance has not been investigated. We evaluated using bi-level positive airway pressure (BIPAP) ventilation assistance for improving respiratory reproducibility in patients with tumor sites impacted by respiratory motion.

Methods: Written informed consent was obtained for 10 patients currently undergoing radiation therapy treatment. Patients participated in sessions over their course of treatment, which …

Semiclassically Modeling Hydrogen At Rydberg States Immersed In Electromagnetic Fields, Jaron Williams

Mathematics Senior Capstone Papers

Originally, closed-orbit theory was developed in order to analyze oscillations in the near ionization threshold (Rydberg) densities of states for atoms in strong external electric and magnetic fields. Oscillations in the density of states were ascribed to classical orbits that began and ended near the atom. In essence, observed outgoing waves following the classical path return and interfere with original outgoing waves, giving rise to oscillations. Elastic scattering from one closed orbit to another gives additional oscillations in the cross-section. This study examines how quantum theory can be properly used in combination with classical orbit theory in order to study …

Sympathetic Physics: The Keely Motor And The Laws Of Thermodynamics In Nineteenth-Century Culture, Robert Macdougall

History Publications

In Philadelphia in the 1870s, John Worrell Keely announced the invention of a fantastic new motor that could, he promised, drive locomotives, power factories, and even defy gravity without fuel or heat. The Keely Motor became the most notorious perpetual motion scheme of the nineteenth century, attracting believers and investors for nearly thirty years. This article explores the “work” the motor performed for Keely, his supporters, and his critics—not physical work, but financial, cultural, and psychological. To investors, the Keely Motor represented a dream of riches without effort. To Keely’s critics, the motor offered an opportunity to defend the legitimacy …

An Investigation Of The Detection Capability Of Pulsed Wave Duplex Doppler Of Low Grade Stenosis Using Ultrasound Contrast Agent Microbubbles – An In-Vitro Study, Jacinta Browne, Deirdre King, Andrew J. Fagan, Deepa Chari, Carmel Moran

Articles

Objective: The objective of the study was to investigate whether clinically used ultrasonic contrast agents improved the accuracy of spectral Doppler ultrasound in the detection of low grade (< 50%) renal artery stenosis. Low grade stenoses in the renal artery are notoriously difficult to reliably detect using Doppler ultrasound due to difficulties such as overlying fat and bowel gas.

Methods: A range of anatomically-realistic renal artery phantoms with varying low degrees of stenosis (0, 30 and 50%) were constructed and peak velocity data was measured from within the pre-stenotic and mid-stenotic regions in each phantom, for both unenhanced and contrast-enhanced spectral Doppler data acquisitions. The effect of a 20mm overlying fat layer on the ultrasound beam distortion and phase aberration, and hence on the measured peak velocity data, was also …

Magnetization Reversal And Local Switching Fields Of Ferromagnetic Co/Pd Microtubes With Radial Magnetization, Norbert Puwenberg, Christopher F. Reiche, Robert Streubel, Mishal Khan, Dipankar Mukherjee, Ivan V. Soldatov, Michael Melzer, Oliver G. Schmidt, Bernd Büchner, Thomas Mühl

Robert Streubel Papers

Three-dimensional nanomagnetism is a rapidly growing field of research covering both noncollinear spin textures and curved magnetic geometries including microtubular structures. We spatially resolve the field-induced magnetization reversal of free-standing ferromagnetic microtubes utilizing multifrequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is …

Determination Of Conversion Factors For Various Calibration Geometries Using Barium-133 In A Silver Zeolite Cartridge, Amin Hamideh

LSU Master's Theses

Iodine-131 (I-131) is a major fission product among other radionuclides released during a nuclear incident. This radioiodine has a half-life of 8.02 days and the primary organ of uptake through ingestion or inhalation is the thyroid gland. For these reasons, nuclear power plants must routinely monitor I-131 through air sampling. Currently, there are two adsorbing media to collect I-131: activated charcoal and silver zeolite cartridges. Silver zeolite cartridges are generally used during a post nuclear incident due to its affinity for iodine while not adsorbing noble gases such as krypton-85 and xenon-135. After an air sample is taken from a …

Analytical Wave Solutions Of The Space Time Fractional Modified Regularized Long Wave Equation Involving The Conformable Fractional Derivative, M. Hafiz Uddin, Md. Ashrafuzzaman Khan, M. Ali Akbar, Md. Abdul Haque

Karbala International Journal of Modern Science

The space time fractional modified regularized long wave equation is a model equation to the gravitational water waves in the long-wave occupancy, shallow waters waves in coastal seas, the hydro-magnetic waves in cold plasma, the phonetic waves in dissident quartz and phonetic gravitational waves in contractible liquids. In nonlinear science and engineering, the mentioned equation is applied to analyze the one way tract of long waves in seas and harbors. In this study, the closed form traveling wave solutions to the above equation are evaluated due to conformable fractional derivatives through double (G'⁄G,1⁄G)-expansion method and the Exp-function method. The existence …

X-Ray Ptychography On Low-Dimensional Hard-Condensed Matter Materials, Xiaowen Shi, Nicolas Burdet, Bo Chen, Gang Xiong, Robert Streubel, Ross Harder, Ian K. Robinson

Robert Streubel Papers

Tailoring structural, chemical, and electronic (dis-)order in heterogeneous media is one of the transformative opportunities to enable new functionalities and sciences in energy and quantum materials. This endeavor requires elemental, chemical, and magnetic sensitivities at the nano/atomic scale in two- and three-dimensional space. Soft X-ray radiation and hard X-ray radiation provided by synchrotron facilities have emerged as standard characterization probes owing to their inherent element-specificity and high intensity. One of the most promising methods in view of sensitivity and spatial resolution is coherent diffraction imaging, namely, X-ray ptychography, which is envisioned to take on the dominance of electron imaging techniques …

University Physics I: Classical Mechanics, Julio Gea-Banacloche

Open Educational Resources

This is a textbook for the first semester of University Physics for scientists and engineers. It covers classical mechanics, and a brief introduction to thermodynamics. The presentation and approach are similar to Mazur’s “The Principles and Practice of Physics,” in that conservation laws are introduced before forces, and one-dimensional systems thoroughly covered before moving to two dimensions. Although the course is “calculus based,” the book has been written with the understanding that many students may be taking calculus simultaneously as a corequisite, so the use of calculus is relatively sparse.

This revised version (Fall 2019) takes into account a number …

Femtosecond-Laser-Induced Spin-Polarized Electron Emission From A Gaas Tip, Evan M. Brunkow, Eric R. Jones, Herman Batelaan, Timothy J. Gay

Timothy J. Gay Publications

It is shown that focusing circularly polarized 800nm light pulses of duration 100 fs on the tips of p-GaAs crystalline shards having no negative electron affinity (NEA) activation results in electron emission that is both fast and spin-polarized. The 400 fs duration of the emission process was determined by pump/probe measurements. The three samples we investigated produced electron polarizations of 13.1(0.9)%, 13.3(0.7)%, and 10.4(0.2)%. Emission currents ranged between 50 pA and 3 nA with a sample bias of –100 V and an average laser power of 100 mW. The electron emission exhibited linear dichroism and was obtained under moderate vacuum …

Viscosities, Diffusion Coefficients, And Mixing Times Of Intrinsic Fluorescent Organic Molecules In Brown Limonene Secondary Organic Aerosol And Tests Of The Stokes–Einstein Equation, Dagny A. Ullmann, Mallory L. Hinks, Adrian M. Maclean, Christopher Butenhoff, James W. Grayson, Kelley Barsanti, Jose L. Jimenez, Sergey A. Nizkorodov, Saeid Kamal, Allan K. Bertram

Physics Faculty Publications and Presentations

Viscosities and diffusion rates of organics within secondary organic aerosol (SOA) remain uncertain. Using the bead-mobility technique, we measured viscosities as a function of water activity (a_w) of SOA generated by the ozonolysis of limonene followed by browning by exposure to NH₃ (referred to as brown limonene SOA or brown LSOA). These measurements together with viscosity measurements reported in the literature show that the viscosity of brown LSOA increases by 3–5 orders of magnitude as the aw decreases from 0.9 to approximately 0.05. In addition, we measured diffusion coefficients of intrinsic fluorescent organic molecules within brown …

Out-Of-Time-Ordered-Correlator Quasiprobabilities Robustly Witness Scrambling, José Raúl González Alonso, Nicole Yunger Halpern, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

Out-of-time-ordered correlators (OTOCs) have received considerable recent attention as qualitative witnesses of information scrambling in many-body quantum systems. Theoretical discussions of OTOCs typically focus on closed systems, raising the question of their suitability as scrambling witnesses in realistic open systems. We demonstrate empirically that the nonclassical negativity of the quasiprobability distribution (QPD) behind the OTOC is a more sensitive witness for scrambling than the OTOC itself. Nonclassical features of the QPD evolve with timescales that are robust with respect to decoherence and are immune to false positives caused by decoherence. To reach this conclusion, we numerically simulate spinchain dynamics and …

Use Of Novel Anthropomorphic Breast Ultrasound Phantoms For Radiology Resident Education, Jacinta Browne, Chris Gu, Robert Fazzio, Andrew J. Fagan, Donald Tradup, Nicholas Hangiandreou

Articles

Purpose: This study evaluated the training and assessment role of anthropomorphic breast ultrasound phantoms which simulated both the morphological and sonographic characteristics of breast tissue, including lesions, in a group of radiology residents at a large academic medical center. Methods: This was a prospective study involving 9 residents across all years (2^nd–4^th year) of a radiology residency program. Baseline assessments of all residents ability to detect and characterize lesions in P-I were carried out, followed by a two-hour teaching session on the same phantom. All residents underwent a post-training, final assessment on P-II to evaluate changes in …

Comforting With Mathematics: A Case Study, Michael J. Goldstein

Journal of Humanistic Mathematics

Death by suicide often leaves behind grieving family members with unanswered questions. Of these concerns, fear that their loved one suffered or felt regret is common. When the method of suicide was jumping from height, that answer can easily be determined using basic kinematics. Despite the perception that mathematics is a cold, calculating field, it can provide a clear, definitive answer and comfort those left behind.

Textured Heterogeneity In Square Artificial Spin Ice, J. C.T. Lee, S. K. Mishra, V. S. Bhat, R. Streubel, B. Farmer, X. Shi, L. E. De Long, I. Mcnulty, P. Fischer, S. D. Kevan, S. Roy

Robert Streubel Papers

We report evidence of spontaneous formation of a heterogeneous network of superdomains in two-dimensional square artificial spin ice nanostructures in externally applied magnetic fields. Coherent resonant soft-x-ray scattering from such textures gives rise to unique internal structure in Bragg peaks. The magnetic heterogeneity is locally disordered but has a zigzag texture at longer length scales. Our result suggests that the macroscopic magnetic texture is derived from the microscopic structure of the Dirac strings.

Boundary Conditions And Berry Phase In Magnetic Nanostructures, A. Ullah, B. Balamurugan, W. Zhang, D. J. Sellmyer, R. Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The effect of micromagnetic boundary conditions on the Berry curvature and topological Hall effect in granular nanostructures is investi- gated by model calculations. Both free surfaces and grain boundaries between interacting particles or grains affect the spin structure. The Dzyaloshinskii-Moriya interactions yield corrections to the Erdmann-Weierstrass boundary conditions, but the Berry curvature remains an exclusive functional of the local spin structure, which greatly simplifies the treatment of nanostructures. An explicit example is a model nanostructure with cylindrical symmetry whose spin structure is described by Bessel function and which yields a mean-field-type Hall-effect contribution that can be related to magnetic-force-microscopy images.

Crystal Structure And Dzyaloshinski–Moriya Micromagnetics, Ahsan Ullah, B. Balamurugan, Wuzhang Fang, Shah R. Valloppilly, Xingzhong Li, Rabindra Pahari, Lanping Yue, Andrei Sokolov, David J. Sellmyer, Ralph Skomski

Nebraska Center for Materials and Nanoscience: Faculty Publications

The relationship between atomic-scale and micromagnetic Dzyaloshinski–Moriya (DM) interactions has been investigated. By analyzing the Lifshitz invariants for different point groups, we have found that there is no unique link between the absence of inversion symmetry and DM interactions. The absence of inversion symmetry is a necessary condition for a net DM interaction in crystals, but several noncentrosymmetric point groups have zero DM interactions. In many cases, the key consideration is whether the crystals are polar and/or chiral. For example, MnSi-type spin spirals, which violate helical spin symmetry, are caused by the insertion of chiral atomic-scale building blocks into an …

Medium-Dependent Antibacterial Properties And Bacterial Filtration Ability Of Reduced Graphene Oxide, Alexander Gusev, Olga Zakharova, Dmitry S. Muratov, Nataliia S. Vorobeva, Mamun Sarker, Iaroslav Rybkin, Daniil Bratashov, Evgeny Kolesnikov, Aleš Lapanje, Denis V. Kuznetsov, Alexander Sinitskii

Nebraska Center for Materials and Nanoscience: Faculty Publications

Toxicity of reduced graphene oxide (rGO) has been a topic of multiple studies and was shown to depend on a variety of characteristics of rGO and biological objects of interest. In this paper, we demonstrate that when studying the same dispersions of rGO and fluorescent Escherichia coli (E. coli) bacteria, the outcome of nanotoxicity experiments also depends on the type of culture medium. We show that rGO inhibits the growth of bacteria in a nutrition medium but shows little effect on the behavior of E. coli in a physiological saline solution. The observed effects of rGO on E. …

Controlling The Magnetocrystalline Anisotropy Of E-Fe2o3, Imran Ahamed, Ralph Skomski, Arti Kashyap

Nebraska Center for Materials and Nanoscience: Faculty Publications

The magnetocrystalline anisotropy of pristine and Co-substituted ε-Fe₂O₃ is investigated by density functional calculations. The epsilon-iron oxide is the only polymorph of Fe₂O₃ magnetoelectric in its antiferromagnetic ground states other crystalline forms being α-Fe₂O₃ (hematite), β-Fe₂O₃, and γ-Fe₂O₃ (maghemite). The magnetizations of the four iron sublattices are antiferromagnetically aligned with slightly different magnetic moments resulting in a ferrimagnetic structure. Compared to the naturally occurring hematite and maghemite, bulk ε-Fe₂O₃ is difficult to prepare, but ε-Fe₂O₃ nanomaterials of different …

High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind gen- erators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of …

High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind generators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of the …

Comparative Study Of Topological Hall Effect And Skyrmions In Nimnin And Nimnga, Wenyong Zhang, Balamurugan Balasubramanian, Ahsan Ullah, Rabindra Pahari, Xingzhong Li, Lanping Yue, Shah R. Valloppilly, Andrei Sokolov, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni2In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by …

Structure And Magnetism Of Co2ge Nanoparticles, Onur Tosun, Frank M. Abel, Balamurugan Balasubramanian, Ralph Skomski, David J. Sellmyer, George C. Hadjipanayis

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural and magnetic properties of Co₂Ge nanoparticles (NPs) prepared by the cluster-beam deposition (CBD) technique have been investigated. As-made particles with an average size of 5.5 nm exhibit a mixture of hexagonal and orthorhombic crystal structures. Thermomagnetic measurements showed that the as-made particles are superparamagnetic at room temperature with a blocking temperature (T_B) of 20 K. When the particles are annealed at 823 K for 12 h, their size is increased to 13 nm and they develop a new orthorhombic crystal structure, with a Curie temperature (T_C) of 815 K. This …

Radiation Tolerance In Nano-Structured Crystalline Fe(Cr)/Amorphous Sioc Composite, Qing Su, Tianyao Wang, Lin Shao, Michael Nastasi

Nebraska Center for Materials and Nanoscience: Faculty Publications

The management of irradiation defects is one of key challenges for structural materials in current and future reactor systems. To develop radiation tolerant alloys for service in extreme irradiation environments, the Fe self-ion radiation response of nanocomposites composed of amorphous silicon oxycarbide (SiOC) and crystalline Fe(Cr) were examined at 10, 20, and 50 displacements per atom damage levels. Grain growth in width direction was observed to increase with increasing irradiation dose in both Fe(Cr) films and Fe(Cr) layers in the nanocomposite after irradiation at room temperature. However, compared to the Fe(Cr) film, the Fe(Cr) layers in the nanocomposite exhibited ~50% …

Magnetic And Magnetocaloric Properties Of Pr2-Xndxfe17 Ribbons, Bishnu Dahal, Parashu Kharel, Thomas Ott, Wenyong Zhang, Shah R. Valloppilly, Ralph Skomski, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The structural, magnetic and magnetocaloric properties of Fe deficient Pr_2-xNd_xFe₁₇ (x = 0.5, 0.7) alloys prepared by arc-melting and melt- spinning have been investigated. The room temperature x-ray diffraction patterns show that the samples are nearly single-phase and crystallize in the rhombohedral Th₂Zn₁₇-type crystal structure. The Curie temperatures determined from the thermomagnetic curves are 302 K and 307 K for Pr_1.5Nd_0.5Fe₁₇ and Pr_1.3Nd_0.7Fe₁₇, respectively. The peak magnetic entropy change and the relative cooling power at field change of 50 kOe …

Quantum Phase Transition And Ferromagnetism In Co1+XSn, Rabindra Pahari, Balamurugan Balasubramanian, Rohit Pathak, Manh Coung Nguyen, Shah R. Valloppilly, Ralph Skomski, Arti Kashyap, Cai-Zhuang Wang, Kai-Ming Ho, George C. Hadjipanayis, David J. Sellmyer

Nebraska Center for Materials and Nanoscience: Faculty Publications

The onset of ferromagnetism in cobalt-tin alloys is investigated experimentally and theoretically. The Co₁₊xSn alloys were prepared by rapid quenching from the melt and form a modified hexagonal NiAs-type crystal structure for 0.45 ≤ x ≤ 1. The magnetic behavior is described analytically and by density-functional theory using supercells and the coherent-potential approximation. The excess of Co concentration x, which enters the interstitial 2d sites in the hypothetical NiAs-ordered parent alloy CoSn, yields a Griffiths-like phase and, above a quantum critical point (x_c ≈ 0.65), a quantum phase …

Theoretical Studies Of The Structure And Stability Of Metal Chalcogenide Crntem (1≤N≤6, 1≤M≤8) Clusters, Fnu Sweta Prabha

Theses and Dissertations

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, Cr_nTe_m clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr₆Te₈ which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation …